processThe Creation
of Caustic I. The creative process leading to Caustic I is typical
of my artwork: a synthesis of research and artistic creation,
each one enhancing the other.
Experimental setup for measuring electron transport (M. Topinka,
B. LeRoy, B. Westervelt) on a micron scale in semiconductor
microstructures, using a charged scanning probe microscope.
Data: Experimental discovery of branching and fringing of electron
flow. The fringes are quantum wave interference effects.
Scientific illustration (with Scot Shaw): Inspired by the experiments,
branch formation is shown to be due to electrons riding over
random hills and depressions in the potential landscape that
they must negotiate. The branching is an indirect effect of
this landscape: branches are not associated simply with valleys
in the landscape.Transport II, the first of a series of large
format high resolution electron flow images using branched flow
physics, revealing the caustics formed when electrons flow from
center image. This image was used for the cover of Nature, March
8, 2001 in connection with the publication of the new results.
The electron flow patterns are remarkably flexible and organic-a
new medium for artistic creation.

Experimentation with various methods of recording individual
electron tracks (overwrite, transparency, color combination)
leads to a variety of effects and expands the horizons of the
medium.
Meanwhile, we begin to wonder about the effects that traveling
in a narrow wire would have on the electron flow. The random,
low hills and valleys are still present, but the additional
confinement to narrow channels leads to new effects-both artistic
and scientific. The first "wire" images are promising:

Color keyed to quantum phase (the wave nature of the electrons)
adds a new dimension to the images. Nanowire is created as a
synthesis of the scientific and artistic experience summarized
here.Inspired by the success of the electron transport images,
which took place in a so-called two dimensional electron gas,
the question of propagation in three dimensions naturally arose.
I decided to look at what happens when light hits a wavy surface;
this of course is becoming commonplace in 3D simulations. But
I needed to know what happens when lights passes through many
successive wavy surfaces. This is the analog of the electrons
traveling over many hills and valleys. Rather than show the
whole path of the light rays, I interrupted them with a plane,
as in a swimming pool bottom. Using a point source of light,
the caustic formation in this case is unfamiliar if there are
many surfaces. In Caustic II there were seven successive surfaces.
This gives remarkable, but perhaps unfamiliar caustic structures.
I began to back off the number of wavy surfaces, for artistic
reasons, mainly.

Caustic I shows light interrupted by the "bottom"
after passing through just two surfaces. Still, the resulting
pattern could not quite be seen on a pool bottom.
There is much room for creative effects, and new physical effects,
in the nature of the waves used on the surface and the number
of surfaces. Caustic I jumped out at me: here was an image almost
like scenes I have seen, full of interesting caustic structures.
I could not resist it!